Jan. 09, 2014

This 100 million-year-old plant survived the ponderous plod of a dinosaur to succumb to an amber tomb. Frozen in time, the specimen is caught in a sexual act: At high magnification, germinating pollen grains are visible entering one of the flower’s stigmas—the first example of a Cretaceous angiosperm in such a configuration. Boasting 18 flowers, it’s also the most complete flowering plant specimen discovered from that time period.

“I don't know of any previous angiosperm flower in a fossil state that has been found with so many flowers on a single sprig," says George Poinar, a professor emeritus in the Department of Integrative Biology at Oregon State University’s College of Science. He co-authored a recent study in the Journal of the Botanical Research Institute of Texas describing the fossil, which was recovered from an amber mine in Myanmar (formerly Burma).

Known as Micropetasos burmensis, the species is new to science and seems to be unrelated to any plant alive today. Viewed at different angles, the fossil offers a detailed perspective of botantical structures and stages of maturity, says Poinar. Its tiny flowers measure less than a millimeter across. There are no petals, only sepals numbering five to a bloom. The pollen, meanwhile, appears to be “sticky,” as Poinar puts it. That is, the grains are attached to flower parts rather than freely floating in the resin, suggesting that this little plant used a pollinator other than wind—perhaps an insect. Indeed, Poinar’s team has previously found a small bee fossil from the same time period, which might have done the work of pollen toting.

At this point in ancient history, terrestrial plant life consisted predominantly of species including gymnosperms (such as cycads and conifers), ferns, moss, and liverworts. M. burmensis represents a period of time when angiosperms were just gaining a foothold toward botanical domination on land.

The dime-size fossil also underscores the value of working with specimens ensconced in amber, says Poinar. “It preserves everything,” he says. “If you look at this [fossil], you'd almost think, Hey, this fell into the resin last week, because everything is so pristine”—from pollen nuclei to anthers, he says. In its demise, this plant achieved immortality.